Wanna know an interesting theory?
Jinbe vs Who's Who is on the 4th floor
Brook/Robin vs Black Maria is on the 3rd floor
Inu vs Jack is on the 2nd floor.
What if any of the fights above breaks 2 floors and causes the fights to be mixed up?
Essentially one scenario could be Jinbe or WsW break the floor below them with some massive Shockwave attack, or another could be Jack doing some insane move that defeats Inu but also breaks the floors above him. Same with Black Maria, maybe she attacks both directions.
Think Kaku falling through the floor with Zoro to Jabra and Usopp. It switched up their fights and led to something else. Jinbe would fall down with WsW. Brook too. Robin stays on the 3rd floor. Maybe if Inu is down, Jinbe realizes he's the strongest needed for Jack, while asking Brook and Robin if they can handle their opponents individually.
This is essentially still one of my two guesses. The other is Yamato being defeated or holding off Kaido long enough for Luffy to return, prompting her eventual fight with Jack. But imo there isn't a feasible way to force her back down exactly to the 2nd floor unless Oda just has Kaido do it by breaking the floors himself to send her back down.
Idk, I'm like 70% sure it's either Jinbe or Yamato. Inu winning doesn't lend itself a lot of confidence. Jack has extremely high recovery, a hidden hybrid, and maybe awakening. I'm not sure how Oda is supposed to make a damaged Inu win.
As for Chopper I'm not sure. I want to see if Page 1 or Ulti get back up first for Usopp and Nami, as Usopp received zero growth moments or had additional focus on his haki. Maybe he joins there, maybe he fights all the Numbers (though I still think those 10 are being reserved for all 10 Scabbards, including Kanjuro, to take them out in big spreads), or maybe he does fight Pero (though I think the theme truly is Strawhats vs Beast Pirates). I am truly stumped by a few of these remaining matchups though, especially Jack, Chopper, Usopp, Page 1, Nami and Ulti.